Known by way of the document DE 101 27 733, for example, is to achieve spiral springs having a good resistance to large-scale thermal stresses as well as good stability in shape. These springs are made up of single-crystal silicon along diverse crystallographic axes. A coating of silicon dioxide can also cover the springs in question.
In addition the document EP 1 422 436 is known describing a method to reduce the thermal drift of a single spiral and thus to achieve a temperature coefficient of zero. This method uses the crystal anisotropy of silicon along one crystallographic axis in relation to another to obtain by way of calculations of thickness of a coating of silicon dioxide making it possible to minimize the thermal coefficients of the spring constant of the spiral spring. The spiral spring described thus ideally comprises a modulation of the thickness. Such a method has, on the one hand, a complexity in its implementation. On the other hand, the spiral springs produced according to this method (i.e. the spiral springs optimized toward a temperature coefficient of zero) do not allow adaptation to different types of balances.